Towel radiator bathroom - electric / heated by hot water?

Hello everyone,

I’ll start my forum membership here with a small question:

We are building a KfW70 house with underfloor heating. In the bathroom on the upper floor, with about 13 sqm, we would like to additionally install a towel radiator to dry towels and temporarily warm the bathroom during the transition seasons. It would therefore only be in operation for a few minutes up to 1 hour per day and only on cool days. We have now been offered 2 alternatives. One is an electric towel radiator and the other is one heated by hot water. Which alternative is recommended in terms of cost and effectiveness?

My (amateur) considerations so far are: With the electric one, you are probably quickly at a 600-watt device, which I find quite high in terms of electricity consumption. The hot water, on the other hand, is already available at a temperature of about 60-65 degrees, but would be drawn from the 300L supply for showering/bathing, so that there could quickly be a bottleneck in a household of 3 people. Or is that unrealistic?

I would be very grateful for advice.

I think you have misunderstood something. Your radiator is definitely not supplied by your drinking water. When warm water is mentioned in this context, it refers to your heating circuit, which, however, provides too low a flow temperature according to the design. The whole thing will then be an expensive towel rail. Nothing more.

An electric heating cartridge makes sense; the power consumption is negligible when considering the usage time. Mostly, in bathrooms, due to the floor heating, recesses in the area of the bathtub and shower make it impossible to achieve the room temperatures assumed in the heating energy calculation. Even with the smallest floor heating pipe spacing.

It was already meant the drinking water. Since, as mentioned, it has a higher flow temperature. But I couldn’t find anything about it on the internet either.

In our case, towel radiators were installed by the general contractor precisely because of the described problem. They operate in the same circuit as the underfloor heating, meaning with low flow temperature, but they have a very large surface area. Whether they are effective, we will only know after the winter.
We probably won't need them at all because the underfloor heating alone is generally sufficient, but it was a matter of calculation. According to this calculation, the prescribed room temperature theoretically could not have been achieved with the underfloor heating alone.
If necessary, the radiators can also be retrofitted with an electric heating cartridge. Sockets for this are also provided on site.

@ClaasC. If it really was the drinking water, I could only imagine it like this: Instead of a pure drinking water tank, you would then use a combination tank and the coil pipes present in the combination tank would be used as a second heating circuit only for the towel radiators. THAT makes sense. Although then a completely separate heating system must be balanced on the pressure side (expansion vessel, valves, etc.) and the tank becomes more "complex." I would definitely recommend the heating cartridge for the few operating hours per year. At least, however, provide a (separately and specially secured) socket within reach! -ks

It was already about the drinking water. Since, as said, it has a higher flow temperature. But I couldn’t find anything about it on the internet either.

Hello there.

So if you want to use the drinking water for your heating, you have several problems:
(1) You can’t reuse the water then – or do you want to drink water that has run through a dirty radiator?? So you channel the water directly from the radiator into the sewer...
(2) You will need a new radiator every 2 years because it will rust through faster than you can blink.

So if your builder really offered you this, you should see to ending the cooperation as soon as possible...

@Häuslebauer40:
If your radiator is connected within the house heating circuit, unfortunately you cannot retrofit an electric heating rod...
How do you want to convince the water not to flow back into the heating circuit but stay in the radiator??
With the heating rod, you would heat your entire heating system...
Effect ~ 0. Costs = huge!

@ClaasCPunkt:
At 600 watts and 1 hour/day and assumed 20 cents/kWh electricity cost: 0.6 kWh * 1h * 0.2 Euro = 0.12 Euro/day

Regards
Micha